Motor assembly

ABSTRACT

A motor assembly includes a motor in a housing. The motor includes a stator and a rotor mounted in the stator casing, and an output shaft engaged with the rotor passes through the stator casing. Two opposite ends of the stator casing and the stator abuts against an annular plate and a rear end cap, respectively. Each screw passes through the rear end cap and the stator to screw into the annular plate, so the stator is fixed and restricted from moving axially in the stator casing. A front end of the housing is engaged with a motor fixing frame. The output shaft passes through a bearing on the motor fixing frame. The motor fixing frame is spaced from the motor. With such design, a vibration of the output shaft during operation is transmitted to the housing, but not directly affect the screws in the motor, thereby increasing the durability of the motor assembly.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates generally to a motor structure, and moreparticularly to a motor assembly that is antishock and easy to assemble.

Description of Related Art

A conventional motor assembly includes a housing, wherein a statorcasing is engaged with the housing. Screws pass through the front endcap, the stator, and the rear end cap to fix the stator in the statorcasing. The stator can generate a magnetic field to drive the rotors inthe housing to rotate, thereby driving the output shaft to rotate.

The front end cap, the stator, and the rear end cap are connected byscrewing to fix the stator of the conventional motor assembly. However,when the motor assembly is mounted in the impact device, the reactionforce is exerted on the output shaft to vibrate during work. Thevibration transmits to the front end cap via the output shaft, so thatthe screws between the front end cap and the stator have to bear theshearing force. Thus, the conventional motor assembly could be easilydamaged, and the life of the conventional motor assembly is reduced.

BRIEF SUMMARY OF THE INVENTION

In view of the above, the primary objective of the present invention isto provide a motor assembly, wherein the motor and the motor fixingframe are separately connected to the housing to avoid fasteners, suchas screws, being damaged by the vibration caused by the reaction force.Additionally, the assembly structure of the motor could be simplified aswell, which facilitates assembly, disassembly, and maintenance.

The present invention provides a motor assembly, including a housing, amotor, and a motor fixing frame. The motor includes a stator casing, astator, an output shaft, a rotor, an annular plate, and a rear end cap.The stator casing is fixed in the housing and is restricted fromrotating along an output shaft, the stator is embedded into the statorcasing. A circumference of the stator has a plurality of through holes.The output shaft passes through a middle of the stator casing. The rotoris engaged with a portion of the output shaft that is surrounded by thestator. The annular plate abuts against an end surface of the statorcasing and an end surface of the stator, and the annular plate has aplurality of screw holes. The rear end cap has a plurality ofperforations and abuts against another end surface of the stator casingand another end surface of the stator. Each of the perforations on therear end cap is inserted by a screw, and each of the screws passesthrough one of the through holes and is screwed into corresponding oneof the screw holes on the annular plate. The rear end cap is disposedwith a rear bearing, and the output shaft passes through the rearbearing. The motor fixing frame is engaged with the end surface of thehousing and has a front bearing, wherein the output shaft passes throughthe front bearing, and the motor fixing frame is spaced from the motor.

With the aforementioned design, the motor fixing frame is spaced awayfrom the motor. When the output shaft is affected by the reaction forceto vibrate, the vibration of the output shaft is transmitted to andabsorbed by the housing, and the screws in the motor do not bear theshearing force, thereby ensuring the motor be used for a long time andnot to be damaged easily. Additionally, during the assembly of themotor, the annular plate should abut against the end surface of thestator first, and the screws connect the stator, the rear end cap, andthe annular plate. The design facilitates assembly, disassembly, andmaintenance.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention will be best understood by referring to thefollowing detailed description of some illustrative embodiments inconjunction with the accompanying drawings, in which

FIG. 1 is a perspective view of the motor assembly of an embodimentaccording to the present invention;

FIG. 2 is an exploded view of the motor assembly of the embodimentaccording to the present invention;

FIG. 3 is an exploded view of the motor assembly of the embodimentaccording to the present invention seen from another perspective;

FIG. 4 is an exploded view of the motor assembly, showing the motorfixing frame is departed;

FIG. 5 is a front view of the motor assembly of the embodiment accordingto the present invention;

FIG. 6 is a sectional view taken along the 6-6 line in FIG. 5 ;

FIG. 7 is an enlarged partial view of a marked region in FIG. 6 ;

FIG. 8 is a sectional view taken along the 8-8 line in FIG. 5 ;

FIG. 9 is a top view of the motor assembly of the embodiment accordingto the present invention; and

FIG. 10 is a sectional view taken along the 10-10 line in FIG. 9 .

DETAILED DESCRIPTION OF THE INVENTION

As illustrated in FIG. 1 to FIG. 8 , a motor assembly 100 of anembodiment according to the present invention includes a housing 10, amotor 20, and a motor fixing frame 30.

The housing 10 has a mounting space 12 inside, and a front end of thehousing 10 that faces the motor fixing frame 30 has an end surface 14.In the current embodiment, the housing 10 is made of plastic andincludes a first shell 16 and a second shell 18, wherein the first shell16 is engaged with the second shell 18 to form the housing 10. In otherembodiments, the housing 10 could be made of other materials, such as acomposite material. Besides, the housing 10 could be integrally formedas a monolithic unit.

The motor 20 is mounted in the mounting space 12 of the housing 10. Themotor 20 includes a stator casing 21, a stator 22, an output shaft 23, arotor 24, an annular plate 25, and a rear end cap 26. The stator casing21 is a cylindrical case. The stator casing 21 is fixed in the housing10 and is restricted from rotating along an axis of the output shaft 23.An inner circumference of the stator casing 21 has a plurality ofrecesses 211, which is spaced.

The stator 22 is embedded into the stator casing 21, and an axis of thestator 22 is aligned with an axis of the stator casing 21. An outercircumference of the stator 22 has a plurality of protruding portions221 which is spaced and corresponds to the recesses 211 of the statorcasing 21. During a process of inserting the stator 22 into the statorcasing 21, the stator 22 is inserted into the stator casing 21 in adirection along the axis of the stator casing 21, and the protrudingportions 221 of the stator 22 are interlocked with the recesses 211 ofthe stator casing 21, so that the stator 22 is unable to rotate relativeto the stator casing 21 after the stator 22 is embedded into the statorcasing 21. Each of the protruding portions 221 of the stator 22 has athrough hole 222, and each of the through hole 222 extends in adirection parallel to the axis of the output shaft 23.

The axis of the stator casing 21 passes through a center of the outputshaft 23. In other words, the axis of the stator casing 21, the axis ofthe stator 22, and the axis of the output shaft 23 are aligned. Therotor 24 is engaged with a portion of the output shaft 23 where issurrounded by the stator 22, wherein the rotor 24 is spaced from thestator 22. The annular plate 25 is a ring-shaped body, wherein theannular plate 25 abuts against an end surface of the stator casing 21and an end surface of the stator 22, and the annular plate 25 has aplurality of screw holes 251. The rear end cap 26 has a plurality ofperforations and abuts against another end surface of the stator casing21 and another end surface of the stator 22, wherein the another endsurface of the stator casing 21 is opposite to the end surface of thestator 22, and another end surface of the stator 22 is opposite to theend surface of the stator 22. Each of the perforations 261 on the rearend cap 26 is inserted by a screw 27. Each of the screws 27 passesthrough one of the through hole 222 and is screwed into correspondingone of the screw holes 251 on the annular plate 25. The stator 22 isclamped between the annular plate 25 and the rear end cap 26 to fix inthe stator casing 21. A rear bearing 262 is embedded in the middle ofthe rear end cap 26, wherein the rear bearing 262 surrounds the outputshaft 23. A rear end of the output shaft 23 passes through the rearbearing 262 on the rear end cap 26.

The motor fixing frame 30 is engaged with the end surface 14 of thehousing 10 by screwing to seal the mounting space 12. The motor fixingframe 30 has a front bearing 32 at the middle of the motor fixing frame30, wherein the front bearing 32 surrounds the output shaft 23. A frontend of the output shaft 23 passes through the front bearing 32 andextends away from the motor fixing frame 30. The motor fixing frame 30is spaced from the motor 20. More specifically, the motor fixing frame30 and the motor 20 do not physically contact each other.

When the motor assembly 100 of the current embodiment is mounted in animpact device, the output shaft 23 connected to a working tool of theimpact device is affected by the reaction force to vibrate during work.Since the motor fixing frame 30 is spaced from the motor 20, thevibration of the output shaft 23 is transmitted through the frontbearing 32 and the motor fixing frame 30 to the housing 10 and isabsorbed by the housing 10, thereby avoiding a shearing force totransmit to the screws 27 to break the screws 27. Thus, even though theoutput shaft 23 of the motor 20 vibrates during an operation for a longtime, the motor 20 is not easy to be broken or damaged.

Additionally, during a process of assembling the motor assembly 100, theannular plate 25 abuts against a front side of the stator 22 and a frontside of the stator casing 21, and then each of the screws 27 is insertedthrough one of the perforations 261 of the rear end cap 26 andcorresponding one of the through holes 222 of the stator 22 to screwinto corresponding one of the screw holes 251 of the annular plate 25,thereby securing the stator 22 in the stator casing 21 to obtain themotor 20. After that, mount the motor 20 to the mounting space 12 of thehousing 10, and then engage the motor fixing frame 30 with the endsurface 14 of the housing 10 to complete the process of assembling themotor assembly 100. With such design, the motor assembly 100 is easy forassembly or disassembly.

As illustrated in FIG. 2 , FIG. 3 , FIG. 9 , and FIG. 10 , the housing10 has a plurality of grooves 11 on an inner surface of the housing 10.In the current embodiment, the housing 10 has two grooves 11. One of thetwo grooves 11 is located in the middle of an inner surface of the firstshell 16, and the other one of the two grooves 11 is located in themiddle of an inner surface of the second shell 18. An outer surface ofthe stator casing 21 has a plurality of blocks 212, wherein a number ofthe plurality of blocks 212 is equal to a number of the plurality ofgrooves 11 on the housing 10, and a location of the blocks 212corresponds to a location of the grooves 11. When the blocks 212 areinserted into the grooves 11, the stator casing 21 is fixed in thehousing 10 and is restricted from rotating and moving in an axialdirection. With such design, the vibration is prevented fromtransmitting in a direction from the housing 10 to the motor 20. Tocontrol an operation of the motor assembly 100, a hall sensor circuitboard 40 is fixed at a rear end of the stator 22 and is located in therear end cap 26, wherein the hall sensor circuit board 40 iselectrically connected to the stator 22 to control a rotational speed ofthe rotors 24 and the output shaft 23.

As illustrated in FIG. 2 to FIG. 4 , an inner side of the end surface ofthe stator casing 21 is recessed to form a step portion 213 and anextending portion 214, wherein the step portion 213 is annular and runsalong the inner circumference of the stator casing 21, the extendingportion 214 is annular and is located at an outer side of the stepportion 213. An axis of the extending portion 214 is concentric with anaxis of the step portion 213. A thickness of the annular plate 25 issmaller than a distance between the end surface of the stator casing 21and the step portion 213. A side of the annular plate 25 abuts againstthe step portion 213 to position.

The motor fixing frame 30 includes a seating plate 34 and a front endcap 36, wherein the seating plate 34 is engaged with the end surface 14of the housing 10 by screwing. The seating plate 34 has a plurality offastening holes 341 located at an edge portion of the seating plate 34.In the current embodiment, each of four corners of the seating plate 34has one fastening hole 341, and the seating plate 34 has a perforation342 at a middle of the seating plate 34. The front end of the outputshaft 23 passes through the perforation 342 of the seating plate 34. Thefront end cap 36 is engaged with an inner side of the seating plate 34,wherein the front end cap 36 is annular, and an axis of the front endcap 36 is aligned with an axis of the perforation 342 of the seatingplate 34. The front end cap 36 has a bearing seat 361 at the middle ofthe front end cap 36. The front end cap 36 has a side wall 362 extendingin a direction away from the seating plate 34. As illustrated in FIG. 6to FIG. 8 , the side wall 362 is annular and extends in a direction fromthe seating plate 34 to the motor 20. When a distal end of the side wall362 is inserted into the step portion 213, the side wall 362 is locatedbetween the seating plate 34 and the annular plate 25, and the distalend of the side wall 362 does not touch the annular plate 25. A part ofthe side wall 362 on the motor fixing frame 30 extends into a spacesurrounded by the extending portion 214, thereby preventing the dustfrom entering through a gap between the side wall 362 and the extendingportion 214 into the stator casing 21. In the current embodiment, a fan231 fits around a portion of the output shaft 23 where is surrounded bythe side wall 362. As the output shaft 23 is rotated, the fan 231 isdriven by the output shaft 23 to rotate and to generate airflow, therebyfacilitating heat dissipation of the motor 20.

It must be pointed out that the embodiment described above is only apreferred embodiment of the present invention. All equivalent structureswhich employ the concepts disclosed in this specification and theappended claims should fall within the scope of the present invention.

What is claimed is:
 1. A motor assembly, comprising: a housing; a motorcomprising a stator casing, a stator, an output shaft, a rotor, anannular plate, and a rear end cap; the stator casing is fixed in thehousing and is restricted from rotating along an output shaft, thestator is embedded into the stator casing; a circumference of the statorhas a plurality of through holes; the output shaft passes through amiddle of the stator casing; the rotor is engaged with a portion of theoutput shaft where is surrounded by the stator; the annular plate abutsagainst an end surface of the stator casing and an end surface of thestator, and the annular plate has a plurality of screw holes; the rearend cap has a plurality of perforations and abuts against another endsurface of the stator casing and another end surface of the stator; eachof the perforations on the rear end cap is inserted by a screw, and eachof the screws passes through one of the through holes and is screwedinto corresponding one of the screw holes on the annular plate; the rearend cap is disposed with a rear bearing, and the output shaft passesthrough the rear bearing; and a motor fixing frame engaged with the endsurface of the housing and having a front bearing, wherein the outputshaft passes through the front bearing, and the motor fixing frame isspaced from the motor.
 2. The motor assembly as claimed in claim 1,wherein the stator casing is fixed in the housing and is restricted frommoving in an axial direction.
 3. The motor assembly as claimed in claim1, wherein the motor fixing frame comprises a seating plate and a frontend cap; the seating plate is engaged with the end surface of thehousing by screwing and has a plurality of fastening holes located at anedge portion of the seating plate; the seating plate has a perforationat a middle of the seating plate, and a front end of the output shaftpasses through the perforations of the seating plate.
 4. The motorassembly as claimed in claim 2, wherein the motor fixing frame comprisesa seating plate and a front end cap; the seating plate is engaged withthe end surface of the housing by screwing and has a plurality offastening holes located at an edge portion of the seating plate; theseating plate has a perforation at a middle of the seating plate, and afront end of the output shaft passes through the perforation of theseating plate.
 5. The motor assembly as claimed in claim 3, wherein aninner side of the end surface of the stator casing is recessed to form astep portion and an extending portion; the step portion is annular, andthe extending portion is annular and is located at an outer side of thestep portion; the annular plate abuts against an inner circumference ofthe extending portion to position.
 6. The motor assembly as claimed inclaim 4, wherein an inner side of the end surface of the stator casingis recessed to form a step portion and an extending portion; the stepportion is annular, and the extending portion is annular and is locatedat an outer side of the step portion; the annular plate abuts against aninner circumference of the extending portion to position.
 7. The motorassembly as claimed in claim 6, wherein the front end cap has a sidewall extending in a direction away from the seating plate; a distal endof the side wall is inserted into the step portion, so that the sidewall is located between the seating plate and the annular plate and isspaced away from the annular plate; when the motor fixing frame isengaged with the motor, the side wall is located in a space surroundedby the extending portion.
 8. The motor assembly as claimed in claim 1,wherein an inner surface of the housing has a plurality of grooves, andan outer surface of the stator casing has a plurality of blocks; each ofthe plurality of blocks is engaged with one of the plurality of groovesto fix and restrict the stator casing in the housing.
 9. The motorassembly as claimed in claim 2, wherein an inner surface of the housinghas a plurality of grooves, and an outer surface of the stator casinghas a plurality of blocks; each of the plurality of blocks is engagedwith one of the plurality of grooves to fix and restrict the statorcasing in the housing.
 10. The motor assembly as claimed in claim 8,wherein the housing comprises a first shell and a second shell, whichare coupled with each other; the inner surface of the housing has twogrooves; one of the two grooves is located on an inner surface of thefirst shell, and the other one of the two grooves is located on an innersurface of the second shell; the outer surface of the stator casing hastwo blocks that are located at a position corresponding to the twogrooves; each of the two blocks is interlocked with one of the twogrooves.
 11. The motor assembly as claimed in claim 9, wherein thehousing comprises a first shell and a second shell, which are coupledwith each other; the inner surface of the housing has two grooves; oneof the two grooves is located on an inner surface of the first shell,and the other one of the two grooves is located on an inner surface ofthe second shell; the outer surface of the stator casing has two blocksthat are located at a position corresponding to the two grooves; each ofthe two blocks is interlocked with one of the two grooves.
 12. The motorassembly as claimed in claim 3, wherein an inner surface of the housinghas a plurality of grooves, and an outer surface of the stator casinghas a plurality of blocks; each of the plurality of blocks is engagedwith one of the plurality of grooves to fix and restrict the statorcasing in the housing.
 13. The motor assembly as claimed in claim 4,wherein an inner surface of the housing has a plurality of grooves, andan outer surface of the stator casing has a plurality of blocks; each ofthe plurality of blocks is engaged with one of the plurality of groovesto fix and restrict the stator casing in the housing.
 14. The motorassembly as claimed in claim 12, wherein the housing comprises a firstshell and a second shell, which are coupled with each other; the innersurface of the housing has two grooves; one of the two grooves islocated on an inner surface of the first shell, and the other one of thetwo grooves is located on an inner surface of the second shell; theouter surface of the stator casing has two blocks that are located at aposition corresponding to the two grooves; each of the two blocks isinterlocked with one of the two grooves.
 15. The motor assembly asclaimed in claim 13, wherein the housing comprises a first shell and asecond shell, which are coupled with each other; the inner surface ofthe housing has two grooves; one of the two grooves is located on aninner surface of the first shell, and the other one of the two groovesis located on an inner surface of the second shell; the outer surface ofthe stator casing has two blocks that are located at a positioncorresponding to the two grooves; each of the two blocks is interlockedwith one of the two grooves.
 16. The motor assembly as claimed in claim1, wherein a hall sensor circuit board is fixed at an end of the statorthat is opposite to the motor fixing frame; the hall sensor circuitboard is located in the rear end cap and is electrically connected tothe stator to control a rotational speed of the rotors and the outputshaft.
 17. The motor assembly as claimed in claim 2, wherein a hallsensor circuit board is fixed at an end of the stator that is oppositeto the motor fixing frame; the hall sensor circuit board is located inthe rear end cap and is electrically connected to the stator to controla rotational speed of the rotors and the output shaft.